DuIK rig interaction

I'm new to creative cow and I need your help for something that I assume should be fairly basic but havent found anywhere. So I have I'm working on a project and they sent me some rigs made with Duik (my first time using the script). Since I have to put more than one character on scene, I'm just duplicating these rig precomps and animating each character on It's own composition so my main comps dont have a thousand layers. It was working flawlessly until I had to make one of this characters grab an object that was, of course, outside the rig precomp. I tried parenting the position and rotation values of the object on my main comp to the pos and rot of the hand of the character inside the rig precomp. It didn't work, I think it is because I have the character scaled down so the movement is not the same. I also realized you cant change precomp's size because it just messes up the rig, so having a single composition with everything apart is not a option and I would think It makes no sense aswell, the precomp workflow I'm using must be the way to go... or not?

Anyways, what's the best way to work with these rigs and how would you make the character grab anything?
Oh and also, what if I want the object be over some parts of the boddy of my rig, but under other ones.